Abstract : Two laboratory experiments were conducted to assess human performance in aligning themselves with linear stimuli. In the first experiment, two point sources of illumination separated by a range of distances were used as stimuli and the subject's task was to align himself with the directional orientation of the aligned pair of 'dots'. In the second experiment, solid lines of different lengths were used as stimuli and the subject's task was to align himself with the directional orientation of the line. Both experiments were conducted in a completely darkened room with the stimuli illuminated by an ultraviolet light. (Author)